<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>图片轮播 js原生(左右切换)</title>
<style type="text/css">
  body,div,ul,li,a,img{margin: 0;padding: 0;}
  ul,li{list-style: none;}
  a{text-decoration: none;}
 
  #wrapper{position: relative;margin: 30px auto;width: 400px;height: 200px;}
  #banner{position:relative;width: 400px;height: 200px;overflow: hidden;}
  .imgList{position:relative;width:2000px;height:200px;z-index: 10;overflow: hidden;}
  .imgList li{float:left;display: inline;}
  #prev,
  #next{position: absolute;top:80px;z-index: 20;cursor: pointer;opacity: 0.2;filter:alpha(opacity=20);}
  #prev{left: 10px;}
  #next{right: 10px;}
  #prev:hover,
  #next:hover{opacity: 0.5;filter:alpha(opacity=50);}
  .bg{position: absolute;bottom: 0;width: 400px;height: 40px;z-index:20;opacity: 0.4;filter:alpha(opacity=40);background: black;}
  .infoList{position: absolute;left: 10px;bottom: 10px;z-index: 30;}
  .infoList li{display: none;}
  .infoList .infoOn{display: inline;color: white;}
  .indexList{position: absolute;right: 10px;bottom: 5px;z-index: 30;}
  .indexList li{float: left;margin-right: 5px;padding: 2px 4px;border: 2px solid black;background: grey;cursor: pointer;}
  .indexList .indexOn{background: red;font-weight: bold;color: white;}
</style>
</head>
<body>
  <div id="wrapper"><!-- 最外层部分 -->
    <div id="banner"><!-- 轮播部分 -->
      <ul class="imgList"><!-- 图片部分 -->
        <li><a href="#"><img src="img/1.jpg" width="400px" height="200px" alt="puss in boots1"></a></li>
      <li><a href="#"><img src="img/2.jpg" width="400px" height="200px" alt="puss in boots2"></a></li>
      <li><a href="#"><img src="img/3.jpg" width="400px" height="200px" alt="puss in boots3"></a></li>
      <li><a href="#"><img src="img/4.jpg" width="400px" height="200px" alt="puss in boots4"></a></li>
      <li><a href="#"><img src="img/1.jpg" width="400px" height="200px" alt="puss in boots5"></a></li>
      </ul>
      <img src="img/prev.png" width="20px" height="40px" id="prev">
      <img src="img/next.png" width="20px" height="40px" id="next">
      <div class="bg"></div> <!-- 图片底部背景层部分-->
      <ul class="infoList"><!-- 图片左下角文字信息部分 -->
        <li class="infoOn">puss in boots1</li>
        <li>puss in boots2</li>
        <li>puss in boots3</li>
        <li>puss in boots4</li>
        <li>puss in boots5</li>
      </ul>
      <ul class="indexList"><!-- 图片右下角序号部分 -->
        <li class="indexOn">1</li>
        <li>2</li>
        <li>3</li>
        <li>4</li>
        <li>5</li>
      </ul>
    </div>
  </div>
  <script type="text/javascript">
  var curIndex = 0, //当前index
      imgArr = getElementsByClassName("imgList")[0].getElementsByTagName("li"), //获取图片组
      imgLen = imgArr.length,
      infoArr = getElementsByClassName("infoList")[0].getElementsByTagName("li"), //获取图片info组
      indexArr = getElementsByClassName("indexList")[0].getElementsByTagName("li"); //获取控制index组
     // 定时器自动变换2.5秒每次
  var autoChange = setInterval(function(){ 
    if(curIndex < imgLen -1){ 
      curIndex ++; 
    }else{ 
      curIndex = 0;
    }
    //调用变换处理函数
    changeTo(curIndex); 
  },2500);
 
  //清除定时器时候的重置定时器--封装
  function autoChangeAgain(){ 
      autoChange = setInterval(function(){ 
      if(curIndex < imgLen -1){ 
        curIndex ++;
      }else{ 
        curIndex = 0;
      }
    //调用变换处理函数
      changeTo(curIndex); 
    },2500);
    }
 
  //调用添加事件处理
  addEvent();
 
  //给左右箭头和右下角的图片index添加事件处理
 function addEvent(){
  for(var i=0;i<imgLen;i++){ 
    //闭包防止作用域内活动对象item的影响
    (function(_i){ 
    //鼠标滑过则清除定时器，并作变换处理
    indexArr[_i].onmouseover = function(){ 
      clearTimeout(autoChange);
      changeTo(_i);
      curIndex = _i;
    };
    //鼠标滑出则重置定时器处理
    indexArr[_i].onmouseout = function(){ 
      autoChangeAgain();
    };
     })(i);
  }
 
  //给左箭头prev添加上一个事件
  var prev = document.getElementById("prev");
  prev.onmouseover = function(){ 
    //滑入清除定时器
    clearInterval(autoChange);
  };
  prev.onclick = function(){ 
    //根据curIndex进行上一个图片处理
    curIndex = (curIndex > 0) ? (--curIndex) : (imgLen - 1);
    changeTo(curIndex);
  };
  prev.onmouseout = function(){ 
    //滑出则重置定时器
    autoChangeAgain();
  };
 
   //给右箭头next添加下一个事件
  var next = document.getElementById("next");
  next.onmouseover = function(){ 
    clearInterval(autoChange);
  };
  next.onclick = function(){ 
    curIndex = (curIndex < imgLen - 1) ? (++curIndex) : 0;
    changeTo(curIndex);
  };
  next.onmouseout = function(){ 
    autoChangeAgain();
  };
}
 
  //左右切换处理函数
  function changeTo(num){ 
    //设置image
    var imgList = getElementsByClassName("imgList")[0];
    goLeft(imgList,num*400); //左移一定距离
    //设置image 的 info
    var curInfo = getElementsByClassName("infoOn")[0];
    removeClass(curInfo,"infoOn");
    addClass(infoArr[num],"infoOn");
    //设置image的控制下标 index
    var _curIndex = getElementsByClassName("indexOn")[0];
    removeClass(_curIndex,"indexOn");
    addClass(indexArr[num],"indexOn");
  }
 
 
  //图片组相对原始左移dist px距离
  function goLeft(elem,dist){ 
    if(dist == 400){ //第一次时设置left为0px 或者直接使用内嵌法 style="left:0;"
      elem.style.left = "0px";
    }
    var toLeft; //判断图片移动方向是否为左
    dist = dist + parseInt(elem.style.left); //图片组相对当前移动距离
    if(dist<0){  
      toLeft = false;
      dist = Math.abs(dist);
    }else{ 
      toLeft = true;
    }
    for(var i=0;i<= dist/20;i++){ //这里设定缓慢移动，10阶每阶40px
      (function(_i){ 
        var pos = parseInt(elem.style.left); //获取当前left
        setTimeout(function(){ 
          pos += (toLeft)? -(_i * 20) : (_i * 20); //根据toLeft值指定图片组位置改变
          //console.log(pos);
          elem.style.left = pos + "px";
        },_i * 25); //每阶间隔50毫秒
      })(i);
    }
  }
 
  //通过class获取节点
  function getElementsByClassName(className){ 
    var classArr = [];
    var tags = document.getElementsByTagName('*');
    for(var item in tags){ 
      if(tags[item].nodeType == 1){ 
        if(tags[item].getAttribute('class') == className){ 
          classArr.push(tags[item]);
        }
      }
    }
    return classArr; //返回
  }
 
  // 判断obj是否有此class
  function hasClass(obj,cls){  //class位于单词边界
    return obj.className.match(new RegExp('(\\s|^)' + cls + '(\\s|$)'));
   }
   //给 obj添加class
  function addClass(obj,cls){ 
    if(!this.hasClass(obj,cls)){ 
       obj.className += cls;
    }
  }
  //移除obj对应的class
  function removeClass(obj,cls){ 
    if(hasClass(obj,cls)){ 
      var reg = new RegExp('(\\s|^)' + cls + '(\\s|$)');
         obj.className = obj.className.replace(reg,'');
    }
  }
 
  </script>
</body>
</html>